Ultra-high dielectric constant garnet

ABSTRACT

Disclosed are embodiments of synthetic garnet materials for use in radiofrequency applications. In some embodiments, increased amounts of bismuth can be added into specific sites in the crystal structure of the synthetic garnet in order to boost certain properties, such as the dielectric constant and magnetization. Accordingly, embodiments of the disclosed materials can be used in high frequency applications, such as in base station antennas.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/459,059, filed Jul. 1, 2019, which is a continuation of U.S. patentapplication Ser. No. 15/715,443, filed Sep. 26, 2017, titled “ULTRA-HIGHDIELECTRIC CONSTANT GARNET”, which is a continuation of U.S. patentapplication Ser. No. 15/181,786, filed Jun. 14, 2016, titled “ULTRA-HIGHDIELECTRIC CONSTANT GARNET”, which claims from the benefit of U.S.Provisional Application No. 62/175,873, filed Jun. 15, 2015, titled“ULTRA HIGH DIELECTRIC CONSTANT GARNET” and U.S. Provisional ApplicationNo. 62/343,685, filed May 31, 2016, titled “ULTRA-HIGH DIELECTRICCONSTANT GARNET,” the entirety of each of which is incorporated hereinby reference.

BACKGROUND Field

The present disclosure generally relates to modified garnets having anultra-high dielectric constant, and applications of such modifiedgarnets.

Description of the Related Art

Various crystalline materials with magnetic properties have been used ascomponents in electronic devices such as cellular phones, biomedicaldevices, and RFID sensors. Garnets are crystalline materials withferrimagnetic properties particularly useful in RF electronics operatingin the lower frequency portions of the microwave region. Many microwavemagnetic materials are derivatives of Yttrium Iron Garnet (YIG), asynthetic form of garnet widely used in various telecommunicationdevices largely because of its favorable magnetic properties such asnarrow linewidth at its ferromagnetic resonance frequency. YIG isgenerally composed of yttrium, iron, and oxygen, and is possibly dopedwith one or more other rare earth metals such as lanthanides orscandium.

SUMMARY

Disclosed herein are embodiments of a synthetic garnet materialcomprising a structure including dodecahedral sites, bismuth occupyingat least some of the dodecahedral sites, the garnet material having adielectric constant value of at least 31.

In some embodiments, the 3 dB linewidth can be less than 100. In someembodiments, the 3 dB linewidth can be less than 80.

In some embodiments, the structure can include gadolinium. In someembodiments, the structure can include gadolinium in a level up to 1.0units. In some embodiments, the synthetic garnet material may notinclude sillenite as a second phase. In some embodiments, the structurecan contain at least 1.4 units of bismuth. In some embodiments, thestructure can contain between 1.4 and 2.5 units of bismuth. In someembodiments, the synthetic garnet material can have a dielectricconstant of at least 34.

Also disclosed herein are embodiments of a synthetic garnet materialcomprising a structure containing at least 1.4 units of bismuthoccupying the dodecahedral sites.

In some embodiments, the synthetic garnet material can have a dielectricconstant of at least 34. In some embodiments, the synthetic garnetmaterial can have a dielectric constant of at least 36. In someembodiments, the structure can contain between 1.4 and 2.5 units ofbismuth. In some embodiments, the garnet material can have amagnetization of 1900 or above.

Also disclosed herein are embodiments of a modified synthetic garnetcomposition represented by the formula:Bi_(x)Ca_(y)Gd_(z)Y_(3-x-y-z)Fe_(5-y)Zr_(y)O₁₂. In some embodiments,0<x<2.5, 0<y<1.0 and 0<z<1.0. In some embodiments, 0<x<2.5, 0<y<1.0 and0<z<2.0. In some embodiments, the modified synthetic garnet compositioncan have a dielectric constant of at least 34. In some embodiments, the3 dB linewidth can be less than 80.

Also disclosed herein are embodiments of a method of manufacturing asynthetic garnet having a high dielectric constant, the methodcomprising providing a yttrium iron garnet structure, inserting greaterthan 1.4 units of bismuth into the iron garnet structure to form amodified synthetic garnet structure without sillenite.

In some embodiments, the modified synthetic garnet can have acomposition of Bi_(x)Ca_(y)Gd_(z)Y_(3-x-y-z)Fe_(5-y)Zr_(y)O₁₂, 0<x<2.5,0<y<1.0 and 0<z<1.0. In some embodiments, 0<x<2.5, 0<y<1.0 and 0<z<2.0.In some embodiments, the modified synthetic garnet can have a dielectricconstant of at least 34. In some embodiments, the modified syntheticgarnet can have 3 dB linewidth of less than 80.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows how materials having one or more featuresdescribed herein can be designed, fabricated, and used.

FIG. 2 depicts an yttrium based garnet crystal lattice structure.

FIG. 3 illustrates an example process flow for making an embodiment of amodified synthetic garnet having one or more features described herein.

FIG. 4 shows an example ferrite device having one or more garnetfeatures as described herein.

FIGS. 5A and 5B show examples of size reduction that can be implementedfor ferrite devices having one or more features as described herein.

FIGS. 6A and 6B show an example circulator/isolator having ferritedevices as described herein.

FIG. 7 shows an example of a packaged circulator module.

FIG. 8 shows an example RF system where one or more ofcirculator/isolator devices as described herein can be implemented.

FIG. 9 shows a process that can be implemented to fabricate a ceramicmaterial having one or more features as described herein.

FIG. 10 shows a process that can be implemented to form a shaped objectfrom powder material described herein.

FIG. 11 shows examples of various stages of the process of FIG. 10.

FIG. 12 shows a process that can be implemented to sinter formed objectssuch as those formed in the example of FIGS. 10 and 11.

FIG. 13 shows examples of various stages of the process of FIG. 12.

FIG. 14 illustrates a perspective view of a cellular antenna basestation incorporating embodiments of the disclosure.

FIG. 15 illustrates housing components of a base station incorporatingembodiments of the disclosed material.

FIG. 16 illustrates a cavity filter used in a base station incorporatingembodiments of the material disclosed herein.

FIG. 17 illustrates an embodiment of a circuit board includingembodiments of the material disclosed herein.

DETAILED DESCRIPTION

Disclosed herein are embodiments of synthetic garnets (or generallyferrites/ferrite garnets), methods of manufacturing them, andapplication so such synthetic garnets. In particular, an excess amountof bismuth atoms can be incorporated into the garnet lattice structurein order to increase the overall dielectric constant of the materialwithout experiencing deleterious effects to other magnetic or electricalaspects of the garnet. In particular, bismuth substituted ferromagneticgarnets may show enhanced dielectric constants as a sintered ceramic,making them especially useful for miniaturizing isolators andcirculators in commercial wireless infrastructure devices, therebyreducing the overall footprint of the devices. Further, the materialscan maintain high magnetization, making them ideal for high frequencyapplications in ranges that have not be feasible before.

FIG. 1 schematically shows how one or more chemical elements (block 1),chemical compounds (block 2), chemical substances (block 3) and/orchemical mixtures (block 4) can be processed to yield one or morematerials (block 5) having one or more features described herein. Insome embodiments, such materials can be formed into ceramic materials(block 6) configured to include a desirable dielectric property (block7), a magnetic property (block 8) and/or an advanced material property(block 9).

In some embodiments, a material having one or more of the foregoingproperties can be implemented in applications (block 10) such asradio-frequency (RF) application. Such applications can includeimplementations of one or more features as described herein in devices12. In some applications, such devices can further be implemented inproducts 11. Examples of such devices and/or products are describedherein.

Synthetic Garnets

Disclosed herein are methods of modifying synthetic garnet compositions,such as Yttrium Iron Garnet (YIG), to increase the dielectric constantof the material. However, it will be understood that other syntheticgarnets, such as yttrium aluminum garnet or gadolinium gallium garnet,can be used as well, and the particular garnet is not limiting. Alsodisclosed herein are synthetic garnet materials having high dielectricconstant (and/or other advantageous properties), methods of producingthe materials, and the devices and systems incorporating such materials.

Synthetic garnets typically have the formula unit of A₃B₅O₁₂, where Aand B are trivalent metal ions. Yttrium Iron Garnet (YIG) is a syntheticgarnet having the formula unit of Y₃Fe₅O₁₂, which includes Yttrium (Y)in the 3+ oxidation state and Iron (Fe) in the 3+ oxidation state. Thegeneral crystal structure of a YIG formula unit is depicted in FIG. 2.As shown in FIG. 2, YIG has a dodecahederal site, an octahedral site,and a tetrahedral site. The Y ions occupy the dodecahedral site whilethe Fe ions occupy the octahedral and tetrahedral sites. Each YIG unitcell, which is cubic in crystal classifications, has eight of theseformula units.

The modified synthetic garnet compositions, in some embodiments, involvesubstituting some or all of the Yttrium (Y) in the Yttrium Iron Garnet(YIG) with one or a combination of other ions such that the resultingmaterial maintains or increases desirable magnetic properties formicrowave (or other) applications, for example high dielectricconstants. There have been past attempts toward doping YIG withdifferent ions to modify the material properties. Some of theseattempts, such as Bismuth (Bi) doped YIG, are described in “MicrowaveMaterials for Wireless Applications” by D. B. Cruickshank, which ishereby incorporated by reference in its entirety. However, in practiceions used as substitutes may not behave predictably because of, forexample, spin canting induced by the magnetic ion itself or by theeffect of non-magnetic ions on the environment adjacent magnetic ions,reducing the degree alignment. Thus, the resulting magnetic propertiescannot be predicted. Additionally, the amount of substitution is limitedin some cases. Beyond a certain limit, the ion will not enter itspreferred lattice site and either remains on the outside in a secondphase compound or leaks into another site. Additionally, ion size andcrystallographic orientation preferences may compete at highsubstitution levels, or substituting ions are influenced by the ion sizeand coordination of ions on other sites. As such, the assumption thatthe net magnetic behavior is the sum of independent sub-lattices orsingle ion anisotropy may not always apply in predicting magneticproperties.

Considerations in selecting an effective substitution of rare earthmetals in YIG for microwave magnetic applications include theoptimization of the density, the magnetic resonance linewidth, thesaturation magnetization, the Curie temperature, the dielectric constantof the material, and the dielectric loss tangent in the resultingmodified crystal structure. Magnetic resonance is derived from spinningelectrons, which when excited by an appropriate radio frequency (RF)will show resonance proportional to an applied magnetic field and thefrequency. The width of the resonance peak is usually defined at thehalf power points and is referred to as the magnetic resonancelinewidth. It is generally advantageous for the material to have a lowlinewidth because low linewidth manifests itself as low magnetic loss,which is required for all low insertion loss ferrite devices. Themodified garnet compositions according to preferred embodiments of thepresent invention provide single crystal or polycrystalline materialswith reduced Yttrium content and yet maintaining low linewidth and otherdesirable properties for microwave magnetic applications.

In some embodiments, a Yttrium based garnet is modified by substitutingBismuth (Bi³⁺) for some of the Yttrium (Y³⁺) on the dodecahedral sitesof the garnet structure in combination with introducing one or moreions, such as divalent (+2), trivalent (+3), tetravalent (+4),pentavalent (+5) or hexavalent (+6) non-magnetic ions to the octahedralsites of the structure to replace at least some of the Iron (Fe³⁺). Insome embodiments, one or more high valency non-magnetic ions such asZirconium (Zr⁴⁺) or Niobium (Nb⁵⁺) can be introduced to the octahedralsites.

In some embodiments, a Yttrium based garnet is modified by introducingone or more high valency ions with an oxidation state greater than 3+ tothe octahedral or tetrahedral sites of the garnet structure incombination with substituting Calcium (Ca²⁺) for Yttrium (Y³⁺) in thedodecahedral site of the structure for charge compensation induced bythe high valency ions, hence reducing the Y³⁺ content. Whennon-trivalent ions are introduced, valency balance is maintained byintroducing, for example, divalent Calcium (Ca²⁺) to balance thenon-trivalent ions. For example, for each 4+ ion introduced to theoctahedral or tetrahedral sites, one Y³⁺ ion can be substituted with aCa²⁺ ion. For each 5+ ion, two Y³⁺ ions can be replaced by Ca²⁺ ions.For each 6+ ion, three Y³⁺ ions can be replaced by Ca²⁺ ions. For each6+ ion, three Y3+ ions can be replaced by Ca²⁺ ions. In one embodiment,one or more high valence ions selected from the group consisting ofZr⁴⁺, Sn⁴⁺, Ti⁴⁺, Nb⁵⁺, Ta⁵⁺, Sb⁵⁺, W⁶⁺, and Mo⁶⁺ is introduced to theoctahedral or tetrahedral sites, and divalent Calcium (Ca²⁺) is used tobalance the charges, which in turn reduces Y3+ content.

In some embodiments, a Yttrium based garnet is modified by introducingone or more high valency ions, such as Vanadium (V⁵⁺), to thetetrahedral site of the garnet structure to substitute for Fe³⁺ tofurther reduce the magnetic resonance linewidth of the resultingmaterial. Without being bound by any theory, it is believed that themechanism of ion substitution causes reduced magnetization of thetetrahedral site of the lattice, which results in higher netmagnetization of the garnet, and by changing the magnetocrystallineenvironment of the ferric ions also reduces anisotropy and hence theferromagnetic linewidth of the material.

In some embodiments, a combination of high Bismuth (Bi) doping combinedwith Vanadium (V) and/or Zirconium (Zr) induced Calcium (Ca) valencycompensation could effectively displace all or most of the Yttrium (Y)in microwave device garnets. Further, certain other high valency ionscould also be used on the tetrahedral of octahedral sites and that afairly high level of octahedral substitution in the garnet structure ispreferred in order to obtain minimized magnetic resonance linewidth.Moreover, Yttrium displacement can be accomplished by adding Calcium inaddition to Bismuth to the dodecahedral site. Doping the octahedral ortetrahedral sites with higher valency ions, preferably greater than 3+,could allow more Calcium to be introduced to the dodecahedral site tocompensate for the charges, which in turn would result in furtherreduction of Yttrium content.

Modified Synthetic Garnet Compositions

Disclosed herein are modified synthetic garnets having very highdielectric constants, while additionally having high magnetizationlevels, making them particularly useful for high frequency applications.In particular, increased amount of Bismuth, along with balancing chargesfrom other elements, can be added into the crystal structure in order toimprove the magnetoelectric properties of the garnet while not reducingother magnetoelectric properties.

In some embodiments, the modified synthetic garnet composition can bedefined by a general composition:Bi_(x)Ca_(y)Gd_(z)Y_(3-xy-z)Fe_(5-y)Zr_(y)O₁₂, where 0≤x≤2.5, 0≤y≤1.0and 0≤z≤1.0. In some embodiments, 0≤x≤2.5, 0≤y≤1.0 and 0≤z≤2.0. In someembodiments, 1.0<x<2.0, 0.1<y<0.8, and 0.2<z<1.9. However, someembodiments of the disclosure may not be defined by the abovecomposition.

In some embodiments, about 1.4 formula units of Bismuth (Bi) can besubstituted for some of the Yttrium (Y) on the dodecahedral site. Insome embodiments, greater than about 1.4 formula units of Bismuth (Bi)can be substituted for some of the Yttrium (Y) on the dodecahedral site.In some embodiments, between about 1.4 and about 2.5 formula units ofBismuth (Bi) can be substituted for some of the Yttrium (Y) on thedodecahedral site. In some embodiments, up to 3.0 formula units ofBismuth (Bi) can be substituted for some of the Yttrium (Y) on thedodecahedral site. The high levels of Bismuth, which can results inadvantageous properties, can be achieved through certain atom inclusionsand methods of manufacturing, as discussed below.

Additionally, as shown for example in the above formula, charge balancecan be achieved by Calcium (Ca) or Zirconium (Zr) substituting for someor all of the remaining Yttrium (Y). In some embodiments, equivalentamounts of Ca and Zr are added to maintain charge stability as Ca has aformal charge of +2 and Zr has a formal charge of +4. Further, in orderto balance the different stresses on the structure caused by theinclusion of Bismuth (Bi), Gadolinium (Gd), or other large rare earthions, can be incorporated into the dodecahedral site of the garnetstructure. For example, Gd may be added to replace the Y, which canimprove temperature stability. Further, the Gd itself can increase thedielectric constant.

Tables 1 below illustrates a list of different synthetic garnetcompositions, as well as their manufacturing parameters. Further, Table2 discloses the corresponding properties achieved by the compositions ofTable 1.

TABLE 1 illustrates a list of compositions and manufacturing parametersNo. Composition 1. Bi_(1.6)Ca_(.65)Y_(.79)Fe_(4.29)Zr_(.65)O_(11.97)950° C./72 h 2. Bi_(1.6)Ca_(.65)Y_(.79)Fe_(4.29)Zr_(.65)O_(11.97) 895°C./100 h 3. Bi_(1.6)Ca_(.65)Gd_(.79)Fe_(4.29)Zr_(.65)O_(11.97) 950°C./72 h 4. Bi_(1.6)Ca_(.65)Gd_(.79)Fe_(4.29)Zr_(.65)O_(11.97) 895°C./100 h 5. Bi_(1.9)Ca_(.65)Gd_(.45)Fe_(4.35)Zr_(.65)O₁₂ 900° C./100 h6. Bi_(1.9)Ca_(.65)Gd_(.45)Fe_(4.35)Zr_(.65)O₁₂ 900° C./100 h 7.Bi_(1.9)Ca_(.65)Gd_(.45)Fe_(4.35)Zr_(.65)O₁₂ 895° C./100 h 8.Bi_(1.9)Ca_(.65)Gd_(.45)Fe_(4.35)Zr_(.65)O₁₂ 895° C./100 h 9.Bi_(1.9)Ca_(.65)Gd_(.45)Fe_(4.35)Zr_(.65)O₁₂

TABLE 2 illustrates properties for the compositions of Table 1Magnetization 3 dB 9 GHz (4πM_(s)) Linewidth Curie Dielectric DielectricPhases Density No. (Gauss) (Oersted) Temp Constant Loss Tangent Present(gkc) 1. 1784  98 33.47 .00306 Garnet 6.007 2. 1812  97 184 34.12 .00290Garnet 6.079 3. 1614  69 183 34.59 .00265 Garnet 6.383 4. 1596  57 17933.89 .00274 Garnet 6.379 5. 1052 505 133 39.2  .00075 Garnet 6.421Perovskite Likely sillenite 6. 1091 370 158 40.6  .00166 Garnet 6.534Perovskite Likely sillenite 7. 1072 347 37.59 .00260 Unknown 6.459 8.1893 316 Unknown 6.322 9. 1050 503 40.74 .00223 Garnet 6.492 Perovskite

As shown in the above table, using embodiments of the disclosedsynthetic garnet, very high dielectric constants can be achieved. Forexample, in some embodiments, the dielectric constant of the syntheticcan be greater than or equal to 31, 33, 35, 37, 39, or 40. Further, the3 dB linewidth can be minimized, with some embodiments having below 100,90, 80, 70, or 60.

The insertion of Bismuth into the garnet structure can cause significantlattice distortion in the garnet structure due to the size of theBismuth being greater than the size of the Yttrium it is replacing.Generally, there is only so much Bismuth that can be inserted into thegarnet structure before the garnet structure decomposes, rendering itless useful for radiofrequency applications. For example, if too muchBismuth is added into the garnet structure, the structure will rejectthe Bismuth, and a Bismuth rich phase, known as sillenite, will form.When sillenite forms, the 3 dB linewidth of the material can greatlyincrease, such as shown in the above Table 2, thus making the materialdifficult for radiofrequency applications.

Sillenite is a structure that is very rich in Bismuth and tends to format the grain boundaries. While the sillenite may not always be detected,as it may form a glass or have poor crystallinity, the 3 dB linewidthusually drastically increases with sillenite, and thus the presence ofsillenite can be assumed with significantly high 3 dB linewidths, suchas shown in compositions 5 and 6 above. Further, anomalously highdielectric constants lead to the assumption that sillenite is present.In addition large 3 dB linewidths may be the result of a defect garnetstructure that has oxygen or cation vacancies.

Due to the difficulty of inserting excess Bismuth into the garnet, otheratoms can be inserted to act as a chemical shim to open up thestructure. For example, Gadolinium (Gd) atoms can be substituted intothe structure, and, due to the greater size of the Gadolinium atoms, amore stable garnet structure can be formed with higher Bismuth contents,allowing for improved properties such as the dielectric constant.Gadolinium, in particular, can have useful magnetic and radiofrequencyproperties. For example, Gadolinium is not a fast relaxer, unlike otherrare earth atoms. Fast relaxers will increase the 3 dB linewidth, due totheir stable 7 f or 4 f electron shells. However, Gadolinium can be usedwithout causing substantial increases in linewidth.

Other large atoms could be used as well instead of Gadolinium, forexample: La, Pr, Nd, Sm, Dy, Yb and Ho. Some of these are fast relaxersand may increase the 3 dB linewidth.

Table III illustrates further synthetic garnet compositions that can beformed using increased amounts of Bismuth in the crystal structure ofthe garnet, along with their respective properties. In some embodiments,Hafnium (Hf) and Titanium (Ti) can be incorporated into the octahedralsites of the lattice. Furthermore, rare earth ions (such as La, Ce, Pr,Nd, Sm, Eu, Dy, Tb, Ho, Er, Tm, Lu and Yb) along with smaller ions (suchMn, In, Sc, Zr, Hf Zn, and Mg) can both be incorporated into thedodecahedral site of the garnet structure. In some cases the totalcharge may need to be balanced with other substitutions.

TABLE III Compositions and properties of synthetic garnets Fired 3 dBDensity Line Dielectric Dielectric Curie Composition (g/cc) widthMagnetization Constant Loss Temp.Bi_(1.4)Ca_(.55)Y_(1.05)Fe_(4.45)Ti_(.55)O₁₂Bi_(1.4)Ca_(.55)Y_(1.05)Fe_(4.45)Zr_(.495)Ti_(.055)O₁₂ 5.439 412 129630.65 0.00324 133.93Bi_(1.4)Ca_(.55)Y_(1.05)Fe_(4.45)Zr_(.44)Ti_(.11)O₁₂ 5.142 749 1175142.19 Bi_(1.4)Ca_(.55)Y_(1.05)Fe_(4.45)Zr_(.385)Ti_(.165)O₁₂ 128.6Bi_(1.4)Ca_(.55)Y_(1.05)Fe_(4.45)Zr_(.33)Ti_(.22)O₁₂ 150.67Bi_(1.4)Ca_(.53)Y_(1.07)Fe_(4.45)Ti_(.53)O_(11.97) 5.849 525 1501 39.380.00233 Bi_(1.4)Sr_(.53)Y_(1.07)Fe_(4.45)Ti_(.53)O_(11.97) 5.655 8651512 27.21 0.00283Bi_(1.4)Ca_(.53)Y_(1.07)Fe_(4.45)Zr_(.26)Ti_(.27)O_(11.97) 5.573 6981422 36.86 0.00199Bi_(1.4)Ca_(.53)Y_(1.07)Fe_(4.45)Zr_(.477)Ti_(.053)O_(11.97) 5.335 2431745 26.67 0.00113Bi_(1.4)Ca_(.53)Y_(1.07)Fe_(4.45)Zr_(.424)Ti_(.106)O_(11.97) 5.359 6651596 19.18 0.00371 Bi_(1.4)Ca_(.53)Y_(1.07)Fe_(4.45)Hf_(.53)O_(11.97)5.71 240 1767 25.86 0.00275Bi_(1.4)Ca_(.53)Y_(1.07)Fe_(4.45)Hf_(.424)Ti_(.106)O_(11.97) 5.564 113628.82 0.00167 Bi_(1.4)Ca_(.26)Sr_(.27)Y_(1.07)Fe_(4.45)Zr_(.53)O_(11.97)5.326 848 1422 28 0.00329Bi_(1.4)Ca_(.26)Sr_(.27)Y_(1.07)Fe_(4.45)Zr_(.26)Ti_(.27)O_(11.97) 4.6391001 26.2 0.00309Bi_(1.4)Ca_(.26)Sr_(.27)Gd_(1.07)Fe_(4.45)Zr_(.53)O_(11.97) 5.676 116529.13 0.00293 Bi_(1.4)Ca_(.53)Y_(1.07)Fe_(4.45)Hf_(.53)O_(11.97) 5.745210 1793 25.28 0.0027Bi_(1.46)Ca_(.53)Y_(1.01)Fe_(4.45)Hf_(.53)O_(11.97) 6.065 102 1884 29.410.00297 Bi_(1.52)Ca_(.53)Y_(0.95)Fe_(4.45)Hf_(.53)O_(11.97) 6.339 441961 Bi_(1.58)Ca_(.53)Y_(0.89)Fe_(4.45)Hf_(.53)O_(11.97) 6.411 59 1951Bi_(1.64)Ca_(.53)Y_(0.83)Fe_(4.45)Hf_(.53)O_(11.97) 6.47 124 1859Bi_(1.7)Ca₅₃Y_(0.77)Fe_(4.45)Hf_(.53)O_(11.97) 6.53 1624 35.33 0.00294Bi_(1.76)Ca_(.53)Y_(0.71)Fe_(4.45)Hf_(.53)O_(11.97) 6.585 365 1528 36.040.00281 Bi_(1.82)Ca_(.53)Y_(0.65)Fe_(4.45)Hf_(.53)O_(11.97) 6.64 2041760 38.03 0.00267 Bi_(1.88)Ca_(.53)Y_(0.59)Fe_(4.45)Hf_(.53)O_(11.97)6.697 447 1407 38.12 0.00254Bi_(1.94)Ca_(.53)Y_(0.53)Fe_(4.45)Hf_(.53)O_(11.97) 6.751 1334 38.990.00216 Bi_(1.75)Ca_(.55)Gd_(0.7)Fe_(4.43)Zr_(.55)O_(11.97) 6.545 2811376 38.79 0.00261 Bi_(1.50)Ca_(.55)Gd_(0.95)Fe_(4.43)Zr_(.55)O_(11.97)6.374 39 1627 33.56 0.00066Bi_(1.50)Ca_(.55)Gd_(0.95)Fe_(4.43)Zr_(.55)O_(11.97) 6.397 22 1648Bi_(1.60)Ca_(.65)Gd_(0.75)Fe_(4.33)Zr_(.65)O_(11.97) 6.353 52 1592 35.620.00208 Bi_(1.60)Ca_(.65)Gd_(0.75)Fe_(4.33)Zr_(.65)O_(11.97) 6.359 511609 Bi_(1.75)Ca_(.55)Gd_(0.7)Fe_(4.43)Zr_(.55)O_(11.97) 6.545 275 138739.2 0.00246 183.66 Bi_(1.70)Ca_(.55)Gd_(0.75)Fe_(4.43)Zr_(.55)O_(11.97)6.497 186 1468 36.85 0.00273 186.15Bi_(1.72)Ca_(.57)Gd_(0.71)Fe_(4.41)Zr_(.57)O_(11.97) 6.53 259 1384 38.40.00254 183.08 Bi_(1.65)Ca_(.55)Gd_(0.80)Fe_(4.43)Zr_(.55)O_(11.97) 6.49156 1515 37.1 0.00275 193.41Bi_(1.67)Ca_(.57)Gd_(0.76)Fe_(4.41)Zr_(.57)O_(11.97) 6.476 166 150536.89 0.00268 188.38Bi_(1.69)Ca_(.59)Gd_(0.72)Fe_(4.39)Zr_(.59)O_(11.97) 6.519 265 140438.15 0.00263 189.92Bi_(1.60)Ca_(.55)Gd_(0.85)Fe_(4.43)Zr_(.55)O_(11.97) 6.461 97 1582 35.460.00287 196.13 Bi_(1.62)Ca_(.57)Gd_(0.81)Fe_(4.41)Zr_(.57)O_(11.97)6.451 114 1562 35.9 0.00283 191.01Bi_(1.64)Ca_(.59)Gd_(0.77)Fe_(4.39)Zr_(.59)O_(11.97) 6.437 124 155135.94 0.00281 186.49Bi_(1.66)Ca_(.61)Gd_(0.73)Fe_(4.37)Zr_(.61)O_(11.97) 6.449 148 150836.15 0.00278 174.22Bi_(1.55)Ca_(.55)Gd_(0.90)Fe_(4.43)Zr_(.55)O_(11.97) 6.417 37 1634 34.790.00224 202 Bi_(1.57)Ca_(.57)Gd_(0.86)Fe_(4.46)Zr_(.57)O_(11.97) 6.41850 1625 35.31 0.00283 190.33Bi_(1.59)Ca_(.59)Gd_(0.82)Fe_(4.49)Zr_(.59)O_(11.97) 6.425 67 1612 35.610.00286 189.38 Bi_(1.61)Ca_(.61)Gd_(0.78)Fe_(4.47)Zr_(.61)O_(11.97)6.419 86 1579 35.97 0.00281 180.05Bi_(1.63)Ca_(.63)Gd_(0.74)Fe_(4.35)Zr_(.63)O_(11.97) 6.414 104 152136.21 0.00282 171.64Bi_(1.50)Ca_(.55)Gd_(0.95)Fe_(4.43)Zr_(.55)O_(11.97) 6.403 31 1649 33.940.00068 200.89 Bi_(1.52)Ca_(.57)Gd_(0.91)Fe_(4.41)Zr_(.57)O_(11.97)6.397 33 1665 33.79 0.00086 195.26Bi_(1.54)Ca_(.59)Gd_(0.87)Fe_(4.39)Zr_(.59)O_(11.97) 6.392 31 1665 34.240.0008 186.62 Bi_(1.56)Ca_(.61)Gd_(0.83)Fe_(4.37)Zr_(.61)O_(11.97) 6.38351 1648 34.89 0.00082 189.99Bi_(1.58)Ca_(.63)Gd_(0.79)Fe_(4.35)Zr_(.63)O_(11.97) 6.381 39 1637 35.990.00161 179.54 Bi_(1.60)Ca_(.65)Gd_(0.75)Fe_(4.33)Zr_(.65)O_(11.97)6.369 34 1634 35.24 0.00211 170.17 Bi_(1.4)Ca_(.6)InZn_(.6)Fe_(4.4)O₁₂6.047 443 1618 31.5 0.0032 Bi_(1.4)Ca_(.6)InMg_(.6)Fe_(4.4)O₁₂ 5.885 4221475 22.98 0.00421 Yb_(1.4)In_(.35)Bi_(1.25)Fe₅O₁₂ 7.047 760 1167 30.490.00278 Yb_(1.05)In_(.70)Bi_(1.25)Fe₅O₁₂ 6.939 781 29.31 0.00051Yb_(.7)In_(1.05)Bi_(1.4)Fe₅O₁₂ 6.636 976 435 25.64 0.00378Yb_(.35)In_(1.4)Bi_(1.25)Fe₅O₁₂ 6.403 142 22.68 0.00438In_(1.75)Bi_(1.25)Fe₅O₁₂ 5.963 25 21.21 0.00468Bi_(1.32)Yb_(1.56)Ca_(.12)Zr_(.12)Fe_(4.88)O₁₂ 7.03 405 1612 30.430.00309 Bi_(1.39)Yb_(1.37)Ca_(.24)Zr_(.24)Fe_(4.76)O₁₂ 6.912 255 177431.59 0.003 Bi_(1.46)Yb_(1.18)Ca_(.36)Zr_(.36)Fe_(4.64)O₁₂ 6.78 187 184231.15 0.00315 Bi_(1.53)Yb_(.99)Ca_(.48)Zr.₄₈Fe_(4.52)O₁₂ 6.623 183 175732.15 0.00297 Bi_(1.6)Yb_(.8)Ca_(.6)Zr_(.6)Fe_(4.4)O₁₂ 6.486 381 166633.51 0.00306 Bi_(1.32)In_(1.56)Ca_(.12)Zr_(.12)Fe_(4.88)O₁₂ 6.125 2726.13 0.00368 Bi_(1.39)In_(1.37)Ca_(.24)Zr_(.24)Fe_(4.76)O₁₂ 6.097 3225.67 0.0028 Bi_(1.46)In_(1.18)Ca_(.36)Zr_(.36)Fe_(4.64)O₁₂ 6.074 3726.48 0.00287 Bi_(1.53)In_(.99)Ca_(.48)Zr_(.48)Fe_(4.52)O₁₂ 6.113 4127.82 0.00356 Bi_(1.6)In_(.8)Ca_(.6)Zr_(.6)Fe_(4.4)O₁₂ 6.14 43 30.760.00245 Bi_(1.6)Yb_(.64)In_(.16)Ca_(.6)Zr_(.6)Fe_(4.4)O₁₂ 6.185 288 91832.42 0.00313 Bi_(1.6)Yb_(.48)In_(.32)Ca_(.6)Zr_(.6)Fe_(4.4)O₁₂ 6.293327 584 33.29 0.00288 Bi_(1.6)Yb_(.32)In_(.48)Ca_(.6)Zr_(.6)Fe_(4.4)O₁₂6.315 326 298 32.45 0.00228Bi_(1.6)Yb_(.16)In_(.64)Ca_(.6)Zr_(.6)Fe_(4.4)O₁₂ 6.217 104 31.17 0.0028Bi_(1.52)Ca_(.53)Y_(0.95)Fe_(4.45)Hf_(.53)O_(11.97) 6.315 42 1954 32.210.0014 Bi_(1.58)Ca_(.53)Y_(0.89)Fe_(4.45)Hf_(.53)O_(11.97) 6.401 58 196032.75 0.00292 Bi_(1.64)Ca_(.53)Y_(0.83)Fe_(4.45)Hf_(.53)O_(11.97) 6.446129 1708 33.42 0.00302

As shown in Table 3, additional elements can be used for the formationof synthetic garnets. For example, hafnium (Hf), strontium (Sr), Indium(In), or Ytterbium can be incorporated into the synthetic garnet forimproved properties. The variations in the compositions can be partiallydue to varied charge balancing schemes. In some embodiments, thematerial may contain some Yttrium. In some embodiments, the material maycontain no Yttrium, for example as the material has been substitutedout.

As shown in the above table, embodiments of the synthetic garnet canachieve very high dielectric constants. For example, embodiments of thesynthetic garnet can achieve dielectric constants of above 35, above 36,or about 38 (or above about 35, above about 36, or above about 38).Accordingly, devices, such as circulators and isolators, can be about 5%to 10% smaller in diameter than a device having a dielectric constant of32. This allows for an overall smaller footprint of the device, allowingfor more of the device to be located in a concentrated area.

Further, embodiments of the disclosure can have very high magnetizationalong with the high dielectric constant, which allows them to be usedover a specific frequency range. As shown above, embodiments of thesynthetic garnet can be above 1600, 1700, 1800, or 1900 (or above about1600, about 1700, about 1800, or about 1900), as opposed to 1500 whichhas been used previously. This allows devices incorporating suchmaterials to be used in higher frequency ranges.

Preparation of the Modified Synthetic Garnet Compositions:

The preparation of the modified synthetic garnet materials can beaccomplished by using known ceramic techniques. A particular example ofthe process flow is illustrated in FIG. 3.

As shown in FIG. 3, the process begins with step 106 for weighing theraw material. The raw material may include oxides and carbonates suchas, for example, Iron Oxide (Fe₂O₃), Bismuth Oxide (Bi₂O₃), YttriumOxide (Y₂O₃), Calcium Carbonate (CaCO₃), Zirconium Oxide (ZrO₂),Gadolinium Oxide (Gd₂O₃), Vanadium Pentoxide (V₂O₅), Yttrium Vanadate(YVO₄), Bismuth Niobate (BiNbO₄), Silica (SiO₂), Niobium Pentoxide(Nb₂O₅), Antimony Oxide (Sb₂O₃), Molybdenum Oxide (MoO₃), Indium Oxide(In₂O₃), or combinations thereof. In some embodiments, raw materialconsisting essentially of about 35-40 wt % Bismuth Oxide, morepreferably about 38.61 wt %; about 10-12 wt % Calcium Oxide, morepreferably about 10.62 wt %; about 35-40 wt % Iron Oxide, morepreferably about 37 wt %, about 5-10 wt % Zirconium Oxide, morepreferably about 8.02 wt %; about 4-6 wt % Vanadium Oxide, morepreferably about 5.65 wt %. In addition, organic based materials may beused in a sol gel process for ethoxides and/or acrylates or citratebased techniques may be employed. Other known methods in the art such asco-precipitation of hydroxides, sol-gel, or laser ablation may also beemployed as a method to obtain the materials. The amount and selectionof raw material depend on the specific formulation.

After the raw materials are weighed, they are blended in Step 108 usingmethods consistent with the current state of the ceramic art, which caninclude aqueous blending using a mixing propeller, or aqueous blendingusing a vibratory mill with steel or zirconia media. In someembodiments, a glycine nitrate or spray pyrolysis technique may be usedfor blending and simultaneously reacting the raw materials.

The blended oxide is subsequently dried in Step 110, which can beaccomplished by pouring the slurry into a pane and drying in an oven,preferably between 100-400° C. or by spray drying, or by othertechniques known in the art.

The dried oxide blend is processed through a sieve in Step 112, whichhomogenizes the powder and breaks up soft agglomerates that may lead todense particles after calcining.

The material is subsequently processed through a pre-sintering calciningin Step 114. Preferably, the material is loaded into a container such asan alumina or cordierite sagger and heat treated in the range of about800-1000° C. In some embodiments, a heat treatment in the range of about500-1000° C. can be used. In some embodiments, a heat treatment in therange of about 900-950° C. can be used. In some embodiments, a heattreatment in the range of about 500-700° C. can be used. Preferably, thefiring temperature is low as higher firing temperatures have an adverseeffect on linewidth.

After calcining, the material is milled in Step 116, preferably in avibratory mill, an attrition mill, a jet mill or other standardcomminution technique to reduce the median particle size into the rangeof about 0.01 to 0.1 microns, though in some embodiments larger sizessuch as 0.5 micron to 10 microns can be used as well. Milling ispreferably done in a water based slurry but may also be done in ethylalcohol or another organic based solvent.

The material is subsequently spray dried in Step 118. During the spraydrying process, organic additives such as binders and plasticizers canbe added to the slurry using techniques known in the art. The materialis spray dried to provide granules amenable to pressing, preferably inthe range of about 10 microns to 150 microns in size.

The spray dried granules are subsequently pressed in Step 120,preferably by uniaxial or isostatic pressing to achieve a presseddensity to as close to 60% of the x-ray theoretical density as possible.In addition, other known methods such as tape casting, tape calendaringor extrusion may be employed as well to form the unfired body.

The pressed material is subsequently processed through a calciningprocess in Step 122. Preferably, the pressed material is placed on asetter plate made of material such as alumina which does not readilyreact with the garnet material. The setter plate is heated in a periodickiln or a tunnel kiln in air or pressure oxygen in the range of betweenabout 850° C.-1000° C. to obtain a dense ceramic compact. In someembodiments, a heat treatment in the range of about 500-1000° C. can beused. In some embodiments, a heat treatment in the range of about500-700° C. can be used. Other known treatment techniques, such asinduction heat, hot pressing, fast firing, or assisted fast firing, mayalso be used in this step. In some embodiments, a density having >98% ofthe theoretical density can be achieved.

The dense ceramic compact is machined in the Step 124 to achievedimensions suitable or the particular applications.

Devices Incorporating Ultra High Dielectric Constant Garnet

Radio-frequency (RF) applications that utilize synthetic garnetcompositions, such as those disclosed above, can include ferrite deviceshaving relatively low magnetic resonance linewidths. RF applications canalso include devices, methods, and/or systems having or related togarnet compositions having reduced or substantially nil reduced earthcontent. As described herein, such garnet compositions can be configuredto yield relatively high dielectric constants; and such a feature can beutilized to provide advantageous functionalities. It will be understoodthat at least some of the compositions, devices, and methods describedin reference above can be applied to such implementations.

FIG. 4 shows a radio-frequency (RF) device 200 having garnet structureand chemistry such as disclosed herein, and thus a plurality ofdodecahedral structures, octahedral structures, and tetrahedralstructures. The device 200 can include garnet structures (e.g., a garnetstructure 220) formed from such dodecahedral, octahedral, andtetrahedral structures. Disclosed herein are various examples of howdodecahedral sites 212, octahedral sites 208, and tetrahedral sites 204can be filled by or substituted with different ions to yield one or moredesirable properties for the RF device 200. Such properties can include,but are not limited to desirable RF properties and cost-effectiveness ofmanufacturing of ceramic materials that can be utilized to fabricate theRF device 200. By way of an example, disclosed herein are ceramicmaterials having relatively high dielectric constants, and havingreduced or substantially nil rare earth contents.

Some design considerations for achieving such features are nowdescribed. Also described are example devices and related RF performancecomparisons. Also described are example applications of such devices, aswell as fabrication examples.

Bismuth Garnets:

Single crystal materials with a formulaBi_((3-2x))Ca_(2x)Fe_(5-x)V_(x)O₁₂ have been grown in the past, where xwas 1.25. A 4πM_(s) value of about 600 Gauss was obtained (which issuitable for some tunable filters and resonators in a 1-2 GHz range),with linewidths of about 1 Oersted, indicating low intrinsic magneticlosses for the system. However, the level of Bi substitution was onlyabout 0.5 in the formula.

Attempts to make single phase polycrystalline materials (with a formulaBi_(3-2x)Ca_(2x)V_(x)Fe_(5-x)O₁₂) similar to the single crystalmaterials were successful only in a region of x>0.96, effectivelyconfining the 4πM_(s) to less than about 700 Oersted and resulting inpoor linewidths (greater than 100 Oersted). Small amounts of Al⁺³reduced the linewidth to about 75 Oersted, but increased Al⁺³ reduced4πM_(s). Bi substitution was only about 0.4 in the formula for thesematerials.

For Faraday rotation devices, the Faraday rotation can be essentiallyproportionate to the level of Bi substitution in garnets, raisinginterest in increasing the level of substitution. Anisotropy isgenerally not a major factor for optical applications, so substitutionon the octahedral and tetrahedral site can be based on maximizing therotation. Thus, in such applications, it may be desirable to introduceas much Bi⁺³ into the dodecahedral site as possible. The maximum levelof Bi⁺³ can be influenced by the size of the dodecahedral rare earthtrivalent ion.

In some situations, the level of Bi⁺³ substitution can be affected bysubstitutions on the other sites. Because Bi⁺³ is non-magnetic, it caninfluence the Faraday rotation through its effect on the tetrahedral andoctahedral Fe⁺³ ions. Since this is thought to be a spin-orbitalinteraction, where Bi⁺³ modifies existing Fe⁺³ pair transitions, one canexpect both a change in the anisotropy of the Fe⁺³ ions and opticaleffects including large Faraday rotation. The Curie temperature of Bi⁺³substituted YIG can also increase at low Bi⁺³ substitution.

Examples of Devices Having Rare Earth Free or Reduced Garnets:

As described herein, garnets having reduced or no rare earth content canbe formed, and such garnets can have desirable properties for use indevices for applications such as RF applications. In someimplementations, such devices can be configured to take advantage ofunique properties of the Bi⁺³ ion. For example, the “lone pair” ofelectrons on the Bi⁺³ ion can raise the ionic polarizability and hencethe dielectric constant.

Further, because the center frequency of a ferrite device (such as agarnet disk) operating in a split polarization transverse magnetic (TM)mode is proportional to 1/(ε)^(1/2), doubling the dielectric constant(ε) can reduce the frequency by a factor of square root of 2(approximately 1.414). As described herein in greater detail, increasingthe dielectric constant by, for example, a factor of 2, can result in areduction in a lateral dimension (e.g., diameter) of a ferrite disk byfactor of square root of 2. Accordingly, the ferrite disk's area can bereduced by a factor of 2. Such a reduction in size can be advantageoussince the device's footprint area on an RF circuit board can be reduced(e.g., by a factor of 2 when the dielectric constant is increased by afactor of 2). Although described in the context of the example increaseby a factor of 2, similar advantages can be realized in configurationsinvolving factors that are more or less than 2.

Reduced Size Circulators/Isolators Having Ferrite with High DielectricConstant

As described herein, ferrite devices having garnets with reduced or norare earth content can be configured to include a high dielectricconstant property. Various design considerations concerning dielectricconstants as applied to RF applications are now described. In someimplementations, such designs utilizing garnets with high dielectricconstants may or may not necessarily involve rare earth freeconfigurations.

Values of dielectric constant for microwave ferrite garnets and spinelscommonly fall in a range of 12 to 18 for dense polycrystalline ceramicmaterials. Such garnets are typically used for above ferromagneticresonance applications in, for example, UHF and low microwave region,because of their low resonance linewidth. Such spinels are typicallyused at, for example, medium to high microwave frequencies, for belowresonance applications, because of their higher magnetization. Most, ifnot substantially all, circulators or isolators that use such ferritedevices are designed with triplate/stripline or waveguide structures.

Dielectric constant values for low linewidth garnets is typically in arange of 14 to 16. These materials can be based on Yttrium iron garnet(YIG) with a value of approximately 16, or substituted versions of thatchemistry with Aluminum or, for example, Zirconium/Vanadium combinationswhich can reduce the value to around 14. Although for example LithiumTitanium based spinel ferrites exist with dielectric constants up toclose to 20, these generally do not have narrow linewidths; and thus arenot suitable for many RF applications. However, as described in detailabove, garnets made using Bismuth substituted for Yttrium can have muchhigher dielectric constants.

In some embodiments, an increase in dielectric constant can bemaintained for compositions containing Bismuth, including those withother non-magnetic substitution on either or both of the octahedral andtetrahedral sites (e.g., Zirconium or Vanadium, respectively). By usingions of higher polarization, it is possible to further increase thedielectric constant. For example, Niobium or Titanium can be substitutedinto the octahedral or tetrahedral site; and Titanium can potentiallyenter both sites.

In some embodiments, a relationship between ferrite device size,dielectric constant, and operating frequency can be represented asfollows. There are different equations that can characterize differenttransmission line representations. For example, in above-resonancestripline configurations, the radius R of a ferrite disk can becharacterized as

R=1.84/[2π(effective permeability)×(dielectric constant)]^(1/2)  (1)

where (effective permeability)=H_(dc)+4πM_(s)/H_(dc), with H_(dc) beingthe magnetic field bias. Equation 1 shows that, for a fixed frequencyand magnetic bias, the radius R is inversely proportional to the squareroot of the dielectric constant.

In another example, in below-resonance stripline configurations, arelationship for ferrite disk radius R similar to Equation 1 can beutilized for weakly coupled quarter wave circulators where the low biasfield corresponds to below-resonance operation. For below-resonancewaveguide configurations (e.g., in disk or rod waveguides), both lateraldimension (e.g., radius R) and thickness d of the ferrite can influencethe frequency. However, the radius R can still be expressed as

R=λ/[2π(dielectric constant)^(1/2)][((πR)/(2d))²+(1.84)²]^(1/2)  (2)

which is similar to Equation 1 in terms of relationship between R anddielectric constant.

The example relationship of Equation 2 is in the context of a circulardisk shaped ferrites. For a triangular shaped resonator, the samewaveguide expression can used, but in this case, A (altitude of thetriangle) being equal to 3.63×λ/2π applies instead of the radius in thecircular disk case.

In all of the foregoing example cases, one can see that by increasingthe dielectric constant (e.g., by a factor of 2), one can expect toreduce the size of the ferrite (e.g., circular disk or triangle) by afactor of square root of 2, and thereby reduce the area of the ferriteby a factor of 2. As described in reference to Equation 2, thickness ofthe ferrite can also be reduced.

In implementations where ferrite devices are used as RF devices, sizesof such RF devices can also be reduced. For example, in a striplinedevice, a footprint area of the device can be dominated by the area ofthe ferrite being used. Thus, one can expect that a correspondingreduction in device size would be achieved. In a waveguide device, adiameter of the ferrite being used can be a limiting factor indetermining size. However, a reduction provided for the ferrite diametermay be offset by the need to retain wavelength-related dimensions in themetal part of the junction.

Examples of Reduced-Size Ferrite

As described herein, ferrite size can be reduced significantly byincreasing the dielectric constant associated with garnet structures.Also as described herein, garnets with reduced Yttrium and/or reducednon-Y rare earth content can be formed by appropriate Bismuthsubstitutions. In some embodiments, such garnets can includeYttrium-free or rare earth free garnets. An example RF device havingferrite devices with increased dielectric constant and Yttrium-freegarnets is described in reference to FIGS. 5A-6B.

FIGS. 5A and 5B summarize the example ferrite size reductions describedherein. As described herein and shown in FIG. 5A, a ferrite device 250can be a circular-shaped disk having a reduced diameter of 2R′ and athickness of d′. The thickness may or may not be reduced. As describedin reference to Equation 1, the radius R of a circular-shaped ferritedisk can be inversely proportional to the square root of the ferrite'sdielectric constant. Thus, the increased dielectric constant of theferrite device 250 is shown to yield its reduced diameter 2R′.

As described herein and shown in FIG. 5B, a ferrite device 250 can alsobe a triangular-shaped disk having a reduced side dimension of S′ and athickness of d′. The thickness may or may not be reduced. As describedin reference to Equation 2, the altitude A of a triangular-shapedferrite disk (which can be derived from the side dimension S) can beinversely proportional to the square root of the ferrite's dielectricconstant. Thus, the increased dielectric constant of the ferrite device250 is shown to yield its reduced dimension S′.

Although described in the context of example circular and triangleshaped ferrites, one or more features of the present disclosure can alsobe implemented in other shaped ferrites.

FIGS. 6A and 6B show an example of a circulator 300 having a pair offerrite disks 302, 312 disposed between a pair of cylindrical magnets306, 316. Each of the ferrite disks 302, 312 can be a ferrite diskhaving one or more features described herein. FIG. 6A shows anun-assembled view of a portion of the example circulator 300. FIG. 6Bshows a side view of the example circulator 300.

In the example shown, the first ferrite disk 302 is shown to be mountedto an underside of a first ground plane 304. An upper side of the firstground plane 304 is shown to define a recess dimensioned to receive andhold the first magnet 306. Similarly, the second ferrite disk 312 isshown to be mounted to an upper side of a second ground plane 314; andan underside of the second ground plane 314 is shown to define a recessdimensioned to receive and hold the second magnet 316.

The magnets 306, 316 arranged in the foregoing manner can yieldgenerally axial field lines through the ferrite disks 302, 312. Themagnetic field flux that passes through the ferrite disks 302, 312 cancomplete its circuit through return paths provided by 320, 318, 308 and310 so as to strengthen the field applied to the ferrite disks 302, 312.In some embodiments, the return path portions 320 and 310 can be diskshaving a diameter larger than that of the magnets 316, 306; and thereturn path portions 318 and 308 can be hollow cylinders having an innerdiameter that generally matches the diameter of the return path disks320, 310. The foregoing parts of the return path can be formed as asingle piece or be an assembly of a plurality of pieces.

The example circulator device 300 can further include an inner fluxconductor (also referred to herein as a center conductor) 322 disposedbetween the two ferrite disks 302, 312. Such an inner conductor can beconfigured to function as a resonator and matching networks to the ports(not shown).

Various examples of new garnet systems and devices related thereto aredescribed herein. In some embodiments, such garnet systems can containhigh levels of Bismuth, which can allow formation of low loss ferritedevices. Further, by selected addition of other elements, one can reduceor eliminate rare earth content of garnets, including commercialgarnets. Reduction or elimination of such rare earth content caninclude, but is not limited to, Yttrium. In some embodiments, the garnetsystems described herein can be configured to significantly increase(e.g., double) the dielectric constant of non-Bi garnets, therebyoffering the possibility of significantly decreasing (e.g., halving) theprinted circuit “footprint” of ferrite devices associated withconventional garnets.

In some embodiments, ferrite-based circulator devices having one or morefeatures as described herein can be implemented as a packaged modulardevice. FIG. 7 shows an example packaged device 400 having a circulatordevice 300 (for example as shown in FIG. 6B) mounted on a packagingplatform 404 and enclosed by a housing structure 402. The exampleplatform 404 is depicted as including a plurality of holes 408dimensioned to allow mounting of the packaged device 400. The examplepackaged device 400 is shown further include example terminals 406 a-406c configured to facilitate electrical connections.

In some embodiments, a packaged circulator/isolator 3002 such as theexample of FIG. 7 can be implemented in a circuit board or module 3004as shown in FIG. 17. Such a circuit board can include a plurality ofcircuits configured to perform one or more radio-frequency (RF) relatedoperations. The circuit board can also include a number of connectionfeatures configured to allow transfer of RF signals and power betweenthe circuit board and components external to the circuit board.

In some embodiments, the foregoing example circuit board can include RFcircuits associated with a front-end module of an RF apparatus. As shownin FIG. 8, such an RF apparatus can include an antenna 512 that isconfigured to facilitate transmission and/or reception of RF signals.Such signals can be generated by and/or processed by a transceiver 514.For transmission, the transceiver 514 can generate a transmit signalthat is amplified by a power amplifier (PA) and filtered (Tx Filter) fortransmission by the antenna 512. For reception, a signal received fromthe antenna 512 can be filtered (Rx Filter) and amplified by a low-noiseamplifier (LNA) before being passed on to the transceiver 514. In theexample context of such Tx and Rx paths, circulators and/or isolators500 having one or more features as described herein can be implementedat or in connection with, for example, the PA circuit and the LNAcircuit.

In some embodiments, circuits and devices having one or more features asdescribed herein can be implemented in RF applications such as awireless base-station. Such a wireless base-station can include one ormore antennas 512, such as the example described in reference to FIG. 8,configured to facilitate transmission and/or reception of RF signals.Such antenna(s) can be coupled to circuits and devices having one ormore circulators/isolators as described herein.

As described herein, terms “circulator” and “isolator” can be usedinterchangeably or separately, depending on applications as generallyunderstood. For example, circulators can be passive devices utilized inRF applications to selectively route RF signals between an antenna, atransmitter, and a receiver. If a signal is being routed between thetransmitter and the antenna, the receiver preferably should be isolated.Accordingly, such a circulator is sometimes also referred to as anisolator; and such an isolating performance can represent theperformance of the circulator.

Fabrication of RF Devices

FIGS. 9-13 show examples of how ferrite devices having one or morefeatures as described herein can be fabricated. FIG. 9 shows a process20 that can be implemented to fabricate a ceramic material having one ormore of the foregoing properties. In block 21, powder can be prepared.In block 22, a shaped object can be formed from the prepared powder. Inblock 23, the formed object can be sintered. In block 24, the sinteredobject can be finished to yield a finished ceramic object having one ormore desirable properties.

In implementations where the finished ceramic object is part of adevice, the device can be assembled in block 25. In implementationswhere the device or the finished ceramic object is part of a product,the product can be assembled in block 26.

FIG. 9 further shows that some or all of the steps of the exampleprocess 20 can be based on a design, specification, etc. Similarly, someor all of the steps can include or be subjected to testing, qualitycontrol, etc.

In some implementations, the powder preparation step (block 21) of FIG.9 can be performed by the example process described in reference to FIG.14. Powder prepared in such a manner can include one or more propertiesas described herein, and/or facilitate formation of ceramic objectshaving one or more properties as described herein.

In some implementations, powder prepared as described herein can beformed into different shapes by different forming techniques. By way ofexamples, FIG. 10 shows a process 50 that can be implemented topress-form a shaped object from a powder material prepared as describedherein. In block 52, a shaped die can be filled with a desired amount ofthe powder. In FIG. 11, configuration 60 shows the shaped die as 61 thatdefines a volume 62 dimensioned to receive the powder 63 and allow suchpower to be pressed. In block 53, the powder in the die can becompressed to form a shaped object. Configuration 64 shows the powder inan intermediate compacted form 67 as a piston 65 is pressed (arrow 66)into the volume 62 defined by the die 61. In block 54, pressure can beremoved from the die. In block 55, the piston (65) can be removed fromthe die (61) so as to open the volume (62). Configuration 68 shows theopened volume (62) of the die (61) thereby allowing the formed object 69to be removed from the die. In block 56, the formed object (69) can beremoved from the die (61). In block 57, the formed object can be storedfor further processing.

In some implementations, formed objects fabricated as described hereincan be sintered to yield desirable physical properties as ceramicdevices. FIG. 12 shows a process 70 that can be implemented to sintersuch formed objects. In block 71, formed objects can be provided. Inblock 72, the formed objects can be introduced into a kiln. In FIG. 13,a plurality of formed objects 69 are shown to be loaded into a sinteringtray 80. The example tray 80 is shown to define a recess 83 dimensionedto hold the formed objects 69 on a surface 82 so that the upper edge ofthe tray is higher than the upper portions of the formed objects 69.Such a configuration allows the loaded trays to be stacked during thesintering process. The example tray 80 is further shown to definecutouts 83 at the side walls to allow improved circulation of hot gas atwithin the recess 83, even when the trays are stacked together. FIG. 13further shows a stack 84 of a plurality of loaded trays 80. A top cover85 can be provided so that the objects loaded in the top tray generallyexperience similar sintering condition as those in lower trays.

In block 73, heat can be applied to the formed objects so as to yieldsintered objects. Such application of heat can be achieved by use of akiln. In block 74, the sintered objects can be removed from the kiln. InFIG. 13, the stack 84 having a plurality of loaded trays is depicted asbeing introduced into a kiln 87 (stage 86 a). Such a stack can be movedthrough the kiln (stages 86 b, 86 c) based on a desired time andtemperature profile. In stage 86 d, the stack 84 is depicted as beingremoved from the kiln so as to be cooled.

In block 75, the sintered objects can be cooled. Such cooling can bebased on a desired time and temperature profile. In block 206, thecooled objects can undergo one or more finishing operations. In block207, one or more tests can be performed.

Heat treatment of various forms of powder and various forms of shapedobjects are described herein as calcining, firing, annealing, and/orsintering. It will be understood that such terms may be usedinterchangeably in some appropriate situations, in context-specificmanners, or some combination thereof.

Telecommunication Base Station

Circuits and devices having one or more features as described herein canbe implemented in RF applications such as a wireless base-station. Sucha wireless base-station can include one or more antennas configured tofacilitate transmission and/or reception of RF signals. Such antenna(s)can be coupled to circuits and devices having one or morecirculators/isolators as described herein.

Thus, in some embodiments, the above disclosed material can beincorporated into different components of a telecommunication basestation, such as used for cellular networks and wireless communications.An example perspective view of a base station 2000 is shown in FIG. 14,including both a cell tower 2002 and electronics building 2004. The celltower 2002 can include a number of antennas 2006, typically facingdifferent directions for optimizing service, which can be used to bothreceive and transmit cellular signals while the electronics building2004 can hold electronic components such as filters, amplifiers, etc.discussed below. Both the antennas 2006 and electronic components canincorporate embodiments of the disclosed ceramic materials.

FIG. 11 shows a schematic view of a base station such as shown in FIG.14. As shown, the base station can include an antenna 412 that isconfigured to facilitate transmission and/or reception of RF signals.Such signals can be generated by and/or processed by a transceiver 414.For transmission, the transceiver 414 can generate a transmit signalthat is amplified by a power amplifier (PA) and filtered (Tx Filter) fortransmission by the antenna 412. For reception, a signal received fromthe antenna 412 can be filtered (Rx Filter) and amplified by a low-noiseamplifier (LNA) before being passed on to the transceiver 414. In theexample context of such Tx and Rx paths, circulators and/or isolators400 having one or more features as described herein can be implementedat or in connection with, for example, the PA circuit and the LNAcircuit. The circulators and isolators can include embodiments of thematerial disclosed herein. Further, the antennas can include thematerials disclosed herein, allowing them to work on higher frequencyranges.

FIG. 15 illustrates hardware 2010 that can be used in the electronicsbuilding 2004, and can include the components discussed above withrespect to FIG. 11. For example, the hardware 2010 can be a base stationsubsystem (BSS), which can handle traffic and signaling for the mobilesystems.

FIG. 16 illustrates a further detailing of the hardware 2010 discussedabove. Specifically, FIG. 16 depicts a cavity filter/combiner 2020 whichcan be incorporated into the base station. The cavity filter 2020 caninclude, for example, bandpass filters such as those incorporatingembodiments of the disclosed material, and can allow the output of twoor more transmitters on different frequencies to be combined.

From the foregoing description, it will be appreciated that an inventivegarnets and method of manufacturing are disclosed. While severalcomponents, techniques and aspects have been described with a certaindegree of particularity, it is manifest that many changes can be made inthe specific designs, constructions and methodology herein abovedescribed without departing from the spirit and scope of thisdisclosure.

Certain features that are described in this disclosure in the context ofseparate implementations can also be implemented in combination in asingle implementation. Conversely, various features that are describedin the context of a single implementation can also be implemented inmultiple implementations separately or in any suitable subcombination.Moreover, although features may be described above as acting in certaincombinations, one or more features from a claimed combination can, insome cases, be excised from the combination, and the combination may beclaimed as any subcombination or variation of any subcombination.

Moreover, while methods may be depicted in the drawings or described inthe specification in a particular order, such methods need not beperformed in the particular order shown or in sequential order, and thatall methods need not be performed, to achieve desirable results. Othermethods that are not depicted or described can be incorporated in theexample methods and processes. For example, one or more additionalmethods can be performed before, after, simultaneously, or between anyof the described methods. Further, the methods may be rearranged orreordered in other implementations. Also, the separation of varioussystem components in the implementations described above should not beunderstood as requiring such separation in all implementations, and itshould be understood that the described components and systems cangenerally be integrated together in a single product or packaged intomultiple products. Additionally, other implementations are within thescope of this disclosure.

Conditional language, such as “can,” “could,” “might,” or “may,” unlessspecifically stated otherwise, or otherwise understood within thecontext as used, is generally intended to convey that certainembodiments include or do not include, certain features, elements,and/or steps. Thus, such conditional language is not generally intendedto imply that features, elements, and/or steps are in any way requiredfor one or more embodiments.

Conjunctive language such as the phrase “at least one of X, Y, and Z,”unless specifically stated otherwise, is otherwise understood with thecontext as used in general to convey that an item, term, etc. may beeither X, Y, or Z. Thus, such conjunctive language is not generallyintended to imply that certain embodiments require the presence of atleast one of X, at least one of Y, and at least one of Z.

Language of degree used herein, such as the terms “approximately,”“about,” “generally,” and “substantially” as used herein represent avalue, amount, or characteristic close to the stated value, amount, orcharacteristic that still performs a desired function or achieves adesired result. For example, the terms “approximately”, “about”,“generally,” and “substantially” may refer to an amount that is withinless than or equal to 10% of, within less than or equal to 5% of, withinless than or equal to 1% of, within less than or equal to 0.1% of, andwithin less than or equal to 0.01% of the stated amount. If the statedamount is 0 (e.g., none, having no), the above recited ranges can bespecific ranges, and not within a particular % of the value. Forexample, within less than or equal to 10 wt./vol. % of, within less thanor equal to 5 wt./vol. % of, within less than or equal to 1 wt./vol. %of, within less than or equal to 0.1 wt./vol. % of, and within less thanor equal to 0.01 wt./vol. % of the stated amount.

Some embodiments have been described in connection with the accompanyingdrawings. The figures are drawn to scale, but such scale should not belimiting, since dimensions and proportions other than what are shown arecontemplated and are within the scope of the disclosed inventions.Distances, angles, etc. are merely illustrative and do not necessarilybear an exact relationship to actual dimensions and layout of thedevices illustrated. Components can be added, removed, and/orrearranged. Further, the disclosure herein of any particular feature,aspect, method, property, characteristic, quality, attribute, element,or the like in connection with various embodiments can be used in allother embodiments set forth herein. Additionally, it will be recognizedthat any methods described herein may be practiced using any devicesuitable for performing the recited steps.

While a number of embodiments and variations thereof have been describedin detail, other modifications and methods of using the same will beapparent to those of skill in the art. Accordingly, it should beunderstood that various applications, modifications, materials, andsubstitutions can be made of equivalents without departing from theunique and inventive disclosure herein or the scope of the claims.

1. (canceled)
 2. A radiofrequency device including a high dielectricgarnet material, the radiofrequency device comprising: a componentformed from a synthetic garnet material having a structure includingdodecahedral sites, the structure having bismuth occupying at least someof the dodecahedral sites for yttrium, the structure having indium, thestructure having a dielectric constant value of at least
 31. 3. Theradiofrequency device of claim 2 further comprising an additional largerare earth ion occupying at least some of the dodecahedral sites.
 4. Theradiofrequency device of claim 3 wherein the additional large rare earthion is ytterbium.
 5. The radiofrequency device of claim 3 wherein theadditional large rare earth ion is gadolinium.
 6. The radiofrequencydevice of claim 2 wherein the structure contains no yttrium as yttriumhas been substituted out.
 7. The radiofrequency device of claim 2wherein the indium occupies at least some of the dodecahedral sites. 8.The radiofrequency device of claim 2 wherein the structure furtherincludes calcium.
 9. The radiofrequency device of claim 8 wherein thestructure further includes zirconium.
 10. The radiofrequency device ofclaim 2 wherein the component is an antenna.
 11. The radiofrequencydevice of claim 2 wherein the component is a circuit board.
 12. Asynthetic garnet material comprising a structure including dodecahedralsites, the structure having bismuth occupying at least some of thedodecahedral sites for yttrium, the structure having indium and adielectric constant value of at least
 31. 13. The synthetic garnetmaterial of claim 12 further comprising an additional large rare earthion occupying at least some of the dodecahedral sites.
 14. The syntheticgarnet material of claim 13 wherein the additional large rare earth ionis ytterbium.
 15. The synthetic garnet material of claim 13 wherein theadditional large rare earth ion is gadolinium.
 16. The synthetic garnetmaterial of claim 12 wherein the indium occupies at least some of thedodecahedral sites.
 17. The synthetic garnet material of claim 12wherein the structure further includes calcium.
 18. The synthetic garnetmaterial of claim 17 wherein the structure further includes zirconium.19. A synthetic garnet material comprising a structure includingdodecahedral sites, the structure having bismuth occupying at least someof the dodecahedral sites, the structure having an additional large rareearth ion occupying at least some of the dodecahedral sites, thestructure having indium.
 20. The synthetic garnet material of claim 19wherein the additional large rare earth ion is ytterbium.
 21. Thesynthetic garnet material of claim 19 wherein the additional large rareearth ion is gadolinium.